Concrete mixers



Oct. 22, 1957 N. E. KERRIDGE 2,810,558

CONCRETE MIXERS 5 Sheets-Sheet 1 Filed Feb. 23, 1956 9W 115 mm Calm-mi BZ,QAw1/w 4-. wig/M I Oct. 22, 1957 N. E. KERRIDC-VIE CONCRETE MIXERS 5 Sheets-Sheet 2 Filed Feb. 25, 1956 Oct. 22, 1957 N. E. KERRIDGE 2 ,810,558

CONCRETE MIXERS Oct. 1957 N. E. KERRIDGE 2,810,558

CONCRETE MIXERS Filed Feb. 23, 1956 5 Sheets-Sheet 4 'Oct. 22, 1957 N. KERRIDGE CONCRETE MIXERS 5 Sheets-Sheet 5 Filed Feb. 23, 1956 Unim SW68 atent CONCRETE MIXERS Norman Edward Kerridge, Salt-ford, near Bristol, England, assignor to Stothert & Pitt Limited, Bath, England, a company of Great Britain Application February 23, 1956, Serial No. 567,393

Claims priority, application Great Britain February 25, 1955 5 Claims. (Cl. 259175) This invention relates to concrete mixers and like mixing machines.

In concrete mixers one of the problems with which the operator is constantly faced is that each time a batch of concrete is discharged from the mixing drum a small deposit remains on the interior surface of the drum and also on the blades or buckets attached to the interior periphery of the drum. With some mixes however much trouble the operator may go to to wash out the drum and keep the buckets or blades clean, it is virtually impossible to do so to prevent a deposit forming on the surfaces of the buckets or blades as the case may be. The result is that concrete will gradually build up on the blades or the buckets and thereby reduce the mixing efliciency of the machine.

Numerous proposals have been made to overcome this problem of the concrete adhering to the metal surfaces of the mixing drum. In one arrangement the mixing chamber and other parts not directly cleaned by the blades of the mixing paddle are provided with an interior-lining of rubber, the presence of the rubber coating, preferably of soft rubber, being intended to prevent the build up of particles of cement which would otherwise occur.

In another proposal, to facilitate cleaning, the interior of the drum is provided with a rubber lining capable of being turned inside out, while in a further proposal the Wall of the drum consists of an endless moving band.

The present invention is concerned with what is known as a free-fall mixer wherein the mixing action is obtained by relatively stationary buckets or blades fixed to the interior of the drum and as the drum revolves the weight of the material being mixed causes it to pour from the buckets or blades, when they reach the upper portion of the drum.

In this type of mixer its range of usefulness has hitherto been restricted since it is dependent upon the mix being sufliciently wet to enable it to flow sufliciently freely since where the proportion of water is low the adhesion is considerably higher thereby preventing it from flowing.

The present invention overcomes this difiiculty by constructing the blades or buckets of flexible material, e. g. rubber, so that the flexure due 'to load and/or material from other buckets falling on those blades or buckets when at the bottom of the mixing drum as thelatter rotates, would operate to prevent or reduce the build-up of concrete on their surfaces.

in carrying out the invention as applied to a non-tilting concrete mixer drum, satisfactory results have been obtained with a construction in which the buckets are each formed throughout of a sheet of rubber moulded or otherwise formed to standard shape, i. e. including a back and sides and secured to the perimeter of the drum by fixing cleats. The rubber, which may vary from %-l" in thickness according to the size of the bucket, may be attached to the cleats by means of large faced washers having means such as a central collar or flange so that when threaded on the fixing bolts with the collars facing inwardly they will act as spacers. It follows that on tightening the nuts of the fixing bolts, the bosses will limit the closing movement and thus grip the rubber firmly before making contact one with the other.

The invention is illustrated in the accompanying drawings in which Figure 1 is a diagrammatic side view of a mixing drum of the non-tilting type, provided with flexing buckets in accordance with the invention.

Figure 2 is a transverse vertical section of the mixing drum showing only two of the buckets,

Figure 2A is a detail view of one of the buckets and showing the fixing means,

Figure 3 is a detail sectional view and Figure 4 an elevation showing the means of fixing the buckets to the drum,

Figures 5-6, 7-8, and 9-10 are respectively a front and end-on view of the buckets showing the deflection produced when leaving sector No. 1 (Figures 5-6); when passing through sector No. 2 (Figures 9-10); and when entering sector No. 1 (Figures 7-8),

Figures 11-12 illustrate the application of the invention to a concrete mixing drum of the tilting type, where the axis of the drum during mixing is mounted to rotate about an axis at an angle to the horizontal and for discharge is tilted to an angle below the horizontal, Figure 11 being a perspective view with part of the wall of the drum broken away to show the interior.

Referring first to Figures 1, 2 and 2A there is shown a mixing drum as fitted to a non-tilting drum mixer, the drum being indicated generally at D and having its axis A-A arranged horizontally, the drum D being provided with a driving band B by which it is caused to rotate. The drum D has annular side walls C providing an inlet opening 01 and a discharge outlet ()2, both the feed of raw material through opening 01 and discharge through the opening 02, being effected by means of a chute, which action of gravity, over buckets or shaped blades, that the range of mixes of concrete that can be mixed efiiciently is limted by the adhesion of the concrete to the buckets and blades preventing it from flowing properly.

According to this invention the buckets or blades within the mixing drum are formed of a material, preferably rubber, so that they are individually capable of flexing during the actual mixing operation, i. e. as the drum revolves. In the arrangement shown in Figures 1 and 2, the buckets indicated generally at 1 are formed of thick sheet rubber (Figure 2A) including a back wall 2 and side walls 3 and 4, the rubber buckets being secured to the inside wall of the drum D by L-shaped cleats 5 (see also Figure 3) and collars 6 having flanges 7 mounted on fixing bolts 8 which are passed through holes in the vertical limbs of the brackets 5. The flanges 7 hereinafter termed the fixing washers, are of sufiicient size to grip the sheet rubber over a fairly wide area so as to prevent the latter being torn away due to load imposed on the rubber, as hereinafter explained. In practice, satisfactory results have been obtained by using four sets of fixing washers, one along each of the side walls 3, 4 and two along the back wall 2. it will be appreciated that the mixing action within the drum D is caused by the buckets 1 picking up the material from the bottom of the drum and after being elevated due to the drum revolving, pouring it when they reach a position near the top. Filling of the buckets commences just as each bucket is leaving sector No. 1. At this point there is little, if any, deflection in the contour of the back and side walls of the bucket due to the weight of material picked up. As the bucket enters sector No. 2, towards the end of which discharge of the contents of the bucket commences, due to the weight of the material bearing against the back wall 2, it is deflected slightly from the normal as indicated by the broken lines in Figures 9 and 10.. and continues in this condition until the contents have been discharged when they fall back to the bottom of the drum.

Due to the constant rotation of the drum it will be appreciated that material is falling downwards to the bottom of the drum in a constant cascade, where, it will encounter empty buckets arriving in sector No. l. The material cascading on to the empty buckets, deflects the free edge of each oncoming bucket forwards and downwards after which it springs back again to its neutral position. This flexing motion of the buckets is shown in Figures 7 and 8 of the drawings, the deflected position being indicated in broken lines, the full line indicating the natural shape of the outer or free edge of the bucket from which it will be seen that the deflection produced is quite appreciable.

During and after the passage of the buckets through sector No. 2 which the buckets enter full of material, it will be appreciated that there is a further deflection of the bucket walls in returning to the normal, due to the release of its contents, and this assists in ejecting from it the remnants of the material in the bucket at a greater velocity than would occur in the case of the normal steel sheet bucket with a rigid wall. On leaving sector No. 2 the buckets pass through sector No. 3 where recovery is complete.

In addition to the constant change in shape of the continuously revolving rubber buckets, the rapid deflection of each bucket and its recovery in sector No. 1 and at the intermediate sector following sector No. 2 will be found to assist mixing by reason of the self cleaning action of the individual buckets due to material being ejected from the buckets at a greater velocity than would apply if gravity were the only force acting on it. This self cleaning action is also apparent on the inside of the drum since the repeated flexing action of the buckets prevents the mix from adhering to the metal surface to the same extent as occurs in the standard type of mixer. I

Referring now to Figure 11 and 12 there is shown a revolving drum tilting mixer, the drum comprising a head section H and a conical portion F, the head H including a hollow Spigot S by means of which it is mounted to rotate, the spigot S in accordance with standard practice being journalled on a shaft or the like (not shown) which is capable of angular adjustment. Angular adjustment, i. e. tilting of the spigot journal and with it the entire mixing drum assembly, from the normal axis of rotation M-M positions the drum for gravity discharge of the contents.

The action of this mixer is that, due to the direction of rotation, a pair of blades 15, 16, carries material up towards the top of the drum where it is cascaded to the charged material falling onto another set of blades, thus causing them to deflect and rectify themselves with a flicking action, thus speeding the mixing action and ridding the blades of build up. Here again the flexible buckets reduce the build up on the inside of the drum shell. 1

It will be found that by fitting concrete mixers with flexible buckets or blades, preferably of thick sheet rubber, in accordance with this invention, it enables the range of concrete mix which can be handled and which depend upon the gravity flow or gravity fall of material to be appreciably extended, by enabling them to mix the more adhesive and less free flowing materials more effectively; by preventing or minimising the build up of material and on the buckets or blades.

What is claimed is:

l. A machine for mixing concrete and like materials comprising a mixing drum, mounted to revolve about a substantially horizontal axis, a series of blade elements formed throughout of flexible sheet material capable of flexing substantially throughout their entireties with change in shape when under load, and means fixing the blade elements to the inside of the periphery of the drum with the major portions of the blade elements extending inwardly toward the center of the drum so as to permit of deflection and change of shape of individual blade elements due to variation in their effective loading as the drum revolves.

2. A machine for mixing concrete and like materials as claimed in claim 1 wherein the means fixing the blade elements to the inside of the periphery of the drum comprise relatively large faced washers.

3. A mixing machine for concrete and like materials, comprising a drum mounted to revolve about a substantiallyhorizontal axis, a-sc'ries of buckets formed of thick sheet rubber so as to be capable of deflection substantially throughout their entiretieswith change in shape under load, and means securing said buckets to the inside of the drum periphery in mutually circumferentially spaced relatipnwith the major portions of said buckets extending inwardly toward the center of the drum to be subject to varyi loads.

4. A machine for mixing concrete and like materials as claimed in claim 3 wherein the means securing the buckets to the inside of the drum periphery comprise relatively large faced washers spaced to permit deflection of the sheet rubber.

5. A machine for mixing concrete and like materials i' as claimed in Claim 3 in which the buckets respectively bottom and again lifted by the oncoming set of blades. In

accordance with this invention, by forming the blades 15, 16 of thick sheet rubber, the blades will assume a difierent shape when carrying the load of material and spring back to normal when it is discharged, the dishave a back wall and side walls, the securing means for the buckets including relatively large faced washers, said washers being spaced one on each of the forward edges of the side Walls and two along the back wall at points adjacent the corners thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

